Hello [expand Cc: a bit] On Tue, Apr 29, 2014 at 12:00:28PM +0200, Uwe Kleine-König wrote: > I grepped through the kernel (v3.15-rc1) for usages of TASK_SIZE to > check if/how it is used on !MMU ARM machines. Most open questions also > affect the other !MMU platforms, so I put the blackfin, c6x, frv and > m32r, m68k, microblaze and xtensa lists on Cc:. (Did I miss a platform > that cares for !MMU ?) > > Most occurences are fine, see the list at the end of this mail. However > some are not or are unclear to me. Here is the complete list[1] apart from > the definition of TASK_SIZE for !MMU in arch/arm/include/asm/memory.h: > > - Probably this should be explict s/TASK_SIZE/CONFIG_DRAM_SIZE/. This > is generic code however while CONFIG_DRAM_SIZE is ARM only. > mm/nommu.c: if (!rlen || rlen > TASK_SIZE) > > - The issue the patch by Rabin is addressing (Subject: [PATCH] ARM: fix > string functions on !MMU), alternatively make TASK_SIZE ~0UL. > arch/arm/include/asm/uaccess.h:#define user_addr_max() \ > arch/arm/include/asm/uaccess.h: (segment_eq(get_fs(), USER_DS) ? TASK_SIZE : ~0UL) [reference: http://www.spinics.net/lists/arm-kernel/msg324112.html ] > - probably bearable if broken: > drivers/misc/lkdtm.c: if (user_addr >= TASK_SIZE) { > lib/test_user_copy.c: user_addr = vm_mmap(...) > lib/test_user_copy.c: if (user_addr >= (unsigned long)(TASK_SIZE)) { > lib/test_user_copy.c: pr_warn("Failed to allocate user memory\n"); > lib/test_user_copy.c: return -ENOMEM; > > - unclear to me: > fs/exec.c: current->mm->task_size = TASK_SIZE; > - depends on PERF_EVENTS > kernel/events/core.c: if (!addr || addr >= TASK_SIZE) > kernel/events/core.c: return TASK_SIZE - addr; > kernel/events/uprobes.c: area->vaddr = get_unmapped_area(NULL, TASK_SIZE - PAGE_SIZE, > - depends on (PERF_EVENTS && (CPU_V6 || CPU_V6K || CPU_V7)): > arch/arm/kernel/hw_breakpoint.c: return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE); > - seems to cope with big TASK_SIZE > fs/namespace.c: size = TASK_SIZE - (unsigned long)data; > fs/namespace.c: if (size > PAGE_SIZE) > fs/namespace.c: size = PAGE_SIZE; > - depends on PLAT_S5P || ARCH_EXYNOS, this looks wrong > drivers/media/platform/s5p-mfc/s5p_mfc_common.h:#define DST_QUEUE_OFF_BASE (TASK_SIZE / 2) > - used for prctl(PR_SET_MM, ...) > kernel/sys.c: if (addr >= TASK_SIZE || addr < mmap_min_addr) > > Any help to judge if these are OK is appreciated (even from Will :-) > > I think it would be OK to define TASK_SIZE to 0xffffffff for !MMU. > blackfin, frv and m68k also do this. c6x does define it to 0xFFFFF000 to > leave space for error codes. > > Thoughts? The problem is that current linus/master (and also next) doesn't boot on my ARM-nommu machine because the user string functions (strnlen_user, strncpy_from_user et al.) refuse to work on strings above TASK_SIZE which in my case also includes the XIP kernel image. Maybe someone of the mm people can bring light into the unclear points above and the question what TASK_SIZE is supposed to be on no-MMU machines? Best regards Uwe > [1] complete as in "skip everything below arch/ but arch/arm" :-) > [removed the list, if you're interested, it's available at http://mid.gmane.org/20140429100028.GH28564@xxxxxxxxxxxxxx] -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ | -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>